The FreeStyle Libre 2 system has three real time optional alarms – no scanning required: 

• Low Glucose Alarm - an alarm will notify you when your glucose falls below a level you set
• High Glucose Alarm - an alarm will notify you when your glucose rises above a level you set
• Signal Loss alarm - an alarm will notify you when the glucose alarms you set are not available because your sensor has lost communication with the app for 20 minutes